Technical Field
The present disclosure generally relates to computed numerically controlled machine tools, and more particularly, to methods and apparatus for performing grind hardening processes using computer controlled machine tools.
Description of the Related Art
Computed Numerically Controlled (CNC) machine tools are generally known for forming metal and wooden parts. Such machine tools include lathes, milling machines, grinding machines, and other tool types. More recently, machining centers have been developed, which provide a single machine having multiple tool types and capable of performing multiple different machining processes. Machining centers may generally include one or more tool retainers, such as spindle retainers and turret retainers holding one or more tools, and a workpiece retainer, such as a pair of chucks. The workpiece retainer may be stationary or move (in translation and/or rotation) while a tool is brought into contact with the workpiece, thereby removing material from the workpiece.
Often, a metal workpiece which has been soft-machined using such machine centers, must undergo a hardening process prior to a grinding or other finishing process. A hardening process typically involves heating, annealing and cooling the metal within a relatively short period of time. Conventional hardening processes use induction coils, gas burners, or the like, in order to heat the metal to temperatures above respective critical temperatures, and subsequently use cooling baths, or the like, to cool the metal to room temperature. The heating and cooling steps of such hardening processes, however, consume significant amounts of energy and resources. Furthermore, the added handling required to remove the soft-machined workpiece from the machine center, harden the workpiece, and reinstall the hardened workpiece back into the machine center for finishing consumes added time and excess labor.
More recent hardening procedures have combined the grinding and hardening processes into a single grind hardening process to overcome some of the drawbacks associated with more conventional hardening techniques. Specifically, the friction that is generated between the grind tool and the workpiece during the grinding process is used to heat the surfaces of the workpiece to temperatures sufficient for hardening. The relatively cooler core of the workpiece then serves as a heat sink which rapidly absorbs the heat from the surface layer to ultimately produce hardening results that are comparable to those of more conventional methods. Although such schemes may provide some improvements, due to the geometry of the grind wheel as well as the manner in which the grind wheel engages a workpiece, currently existing grind hardening processes are unable to provide uniform or adequately controlled hardened surfaces. Furthermore, existing schemes lack measures for monitoring a hardening process, and thus, are unable to more finely control the degree of hardness that is applied to a work surface. Currently existing schemes also use an excess of energy and resources in order to cool or clean the contact area between the grind tool and the workpiece during a grind hardening process.